Conventional dual time-base oscilloscopes such as disclosed in U.S. Pat. Nos. 4,551,656 to Metz and U.S. Pat. No. 4,109,182 to Dalton have two sweep or ramp generators for generating a main sweep and a delayed sweep. The starting point for the delayed sweep may be selected at any time point along the main sweep. This delayed starting point enables the delayed sweep to expand the selected main sweep segment for visual measurement of a pulse or other event of interest within the segment using the lined graticule on the oscilloscope cathode ray tube (CRT). For example, to measure the timing parameters of a pulse, such as its period, the delayed sweep can be set to display the pulse in expanded form for higher resolution on the graticule. The drawback of this measurement technique, of course, is the error inherent in visually calculating values from a graticule. This is particularly true when the widths of the electron beam and the graticule lines are large relative to the resolution desired.